<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
    var a=20;
    var b="20";
    var c=20;

    alert(a==b);
    alert(a===b);
    alert(a===c);

    alert(parseInt("12A45"));//12
    alert(parseInt("A45"));//NaN
//0,NaN,"",undifine传唤成boolean时为false,其他为true;
</script>
</html>